1. Field of the Invention
The present invention is directed to improved insulation panels for furnaces and to the corresponding method of forming such insulation panels. The present invention includes an insulated furnace assembly which utilizes the concept of a plurality of interconnected modular panels of fibrous material which serve to form and insulate a furnace chamber and to provide a thermal break of 10.degree. to 30.degree. F. between an outside surface portion of the insulation panel and the shell of the furnace. A method of removing residual air and water vapor from the furnace for subsequent operation is also utilized in the present invention.
2. Description of the Prior Art
Conventional refractory furnaces for the processing of steel, etc. usually use brick as an insulating material. Brick insulation has been found, however, to have a number of drawbacks including the fact that its use makes it impossible to quickly start up the furnace. Since initial start-up time is generally on the order of two weeks with brick insulation, it is necessary to gradually raise the heat within the furnace to remove residual gases in the form of air and water vapor. In other words, rapidly attempting to heat up and purge a conventional furnace may result in exceeding the exterior brick wall temperature standards established by the Occupational Safety and Health Administration and destruction of the brick insulation and the steel structure of the furnace itself which results in greater furnace down-time in repairing the brick structure. The problem with purging brick insulation is that the internal structure of brick is such that pockets of air formed therein are cellular in nature and not interconnected and it is therefore difficult to purge air and water vapor from the bricks themselves. More particularly, heating of the brick walled furnace interior can effectively remove only the air and water vapor collecting in pockets, formed in the brick when the brick itself was made, positioned on the interior surface of the brick or immediately adjacent thereto. Attempts to more effectively purge the brick furnace of air and water vapor by increasing the heat has merely resulted in a high incidence of structural failure of the brick itself and, for this reason, companies which operate such furnaces must then resort to employing a large number of highly skilled and relatively expensive brick layers to reconstruct the brick wall of the furnace. Even more importantly, structural failure of the brick results in a shut-down of the furnace for extended periods of time to allow for repair or complete reconstruction of the brick walls.
The process of initially purging a brick walled furnace also typically requires the use of purging gas to drive the water vapor and air out of the exhaust flue, a large percentage being first driven to the exterior or cold wall portion of the furnace and this required as much as six complete atmospheric changes per hour to effectively remove the air and moisture. The number of atmospheric changes required thus significantly contributed to the requirements of an approximately two week time period for purging of a new brick walled furnace.
Insofar as the drawback of using brick as insulation in a protective atmosphere furnace is that it is difficult to start up the furnace, such furnaces are usually continuously run even during the time periods within which steel is not being processed therein. To do otherwise would allow air and water vapor to again collect in the pockets formed in the brick and thus necessitate a renewed purging of the furnace in the manner described hereinabove. Accordingly, the cost of operating such conventional furnaces is quite high based upon the continuous use of energy even when steel is not being processed.
Another drawback of conventional brick insulation furnace is the fact that upon attempting to purge the furnace, water vapor tends to migrate away from the heat source within the furnace and towards the exterior wall of the brick insulation.